通过固态NMR光谱学观察到的皮里多-5'-酸盐-酶模型系统中功能性键的合
Shasad Sharif1, David Schagen, Michael D Toney
1Institut für Chemie und Biochemie, Takustrasse 3, Freie Universität Berlin, D-14195 Berlin, Germany.
Journal of the American Chemical Society
|March 21, 2007
概括
新的Schiff基模型的pyridoxal-5'-phosphate (PLP) 与碳氧酸揭示了对酶辅因子活性至关重要的合质子转移. 这种质子转移取决于希夫基原子上的替代物.
科学领域:
- 生物物理化学 生物物理化学
- 结构生物学 结构生物学
- 有机化学 有机化学
背景情况:
- 皮里多-5-酸盐 (PLP) 是许多酶反应中的重要辅助因子.
- 了解PLP的机制需要研究模拟其活动部位的模型系统.
- 键在生物分子的功能中起着至关重要的作用.
研究的目的:
- 合成和描述新型的与酸结合的 Schiff 基模型的与酸结合的 PLP 复合物.
- 为了研究这些模型系统中的质子转移动态.
- 阐明影响辅助因子活动的结构和电子因素.
主要方法:
- 希夫基模型的合成,包括N-pyridoxylidene-tolylamine和N-pyridoxylidene-methylamine添加物.
- 15N交叉极化 (CP) 和1H核磁共振 (NMR) 光谱在静态和魔法角度旋转 (MAS) 条件下.
- 用X射线晶体学,1H/15N化学转移相关性,二次H/D同位素效应和2H-15N双极合进行结构分析.
主要成果:
- 新的多晶1:1复合体的PLP希夫基模型与碳酸酸被成功合成.
- 描述揭示了合的分子内和分子间OHN键与快速质子共聚.
- 皮里丁环的质子化诱导了质子在分子内键中的转移,当在希夫基上存在一个异形替代物时.
结论:
- 观察到的联质子转移,模仿了PLP在酶活性位点中的行为,取决于希夫基的替代物的性质.
- 这种合的质子转移,导致希夫基的正电荷增加,被认为是辅因子活动的先决条件.
- 该研究通过对定义良好的模型系统的调查,为PLP依赖酶的基本机制提供了宝贵的见解.
相关概念视频
02:21Globular and Fibrous Proteins
Many proteins can be classified into two distinct subtypes - globular or fibrous. These two types differ in their shapes and solubilities.
Globular proteins are also known as spheroproteins and typically are approximately round in shape. They contain a mix of amino acid types and contain differing sequences in their primary structures. Globular proteins have many different functions, such as enzymes, cellular messengers, and molecular transporters. These roles often require the proteins to be...
Globular proteins are also known as spheroproteins and typically are approximately round in shape. They contain a mix of amino acid types and contain differing sequences in their primary structures. Globular proteins have many different functions, such as enzymes, cellular messengers, and molecular transporters. These roles often require the proteins to be...
00:49Ligand Binding and Linkage
Allosteric proteins have more than one ligand binding site; the binding of a ligand to any of these sites influences the binding of ligands to the other sites. When a protein is allosteric, its binding sites are called coupled or linked. In the case of enzymes, the site that binds to the substrate is known as the active site and the other site is known as the regulatory site. When a ligand binds to the regulatory site, this leads to conformational changes in the protein that can influence the...
01:30NMR and Mass Spectroscopy of Carboxylic Acids
In ¹H NMR spectroscopy, acidic protons (–COOH) of carboxylic acids are highly deshielded and absorb far downfield, at around 9–12 ppm. The chemical shift value depends on the concentration and solvent used.
While α protons of carboxylic acids absorb at 2–2.5 ppm, β protons absorb further upfield.
Carboxylic acids are easily identified by dissolving them in deuterium oxide, which results in a rapid exchange of the acidic protons with deuterium. This leads to the disappearance of the acidic...
While α protons of carboxylic acids absorb at 2–2.5 ppm, β protons absorb further upfield.
Carboxylic acids are easily identified by dissolving them in deuterium oxide, which results in a rapid exchange of the acidic protons with deuterium. This leads to the disappearance of the acidic...
01:19NMR Spectroscopy Of Amines
In proton NMR spectroscopy, primary amines and secondary amines showcase their N–H protons as a broad signal in the chemical shift range between δ 0.5 and 5 ppm. The exact position in this range depends on several factors, including sample concentration, hydrogen bonding, and the type of solvent used. Since amine protons undergo fast proton exchange in solution, the protons are labile and therefore do not participate in any splitting with adjacent protons. Thus, the observed peak is broad and...